NATURAL SCIENCES OF PHILADELPHIA. 33 



even to the wings and tail ; the continuity of the white only interrupted by a 

 few isolated brown featbei s sparsely scattered at irregular intervals over the 

 body. Other specimens in the Academy Museum are in very nearly the 

 plumage described by Gmelin and Latham as P. Brasiliana ; so that there can 

 be little doubt of the propriety of relerring the latter to tiiis species.* 



The species and genera treated of in this paper are so few and so well known 

 that an analytical synopsis does not seem to be required. 



(To he continued,') 



Description of twelve new species of UNIONIDJS from South America. 



BY ISAAC LEA. 



The species described and figured in this paper were procured in South 

 America by Don Prttricio M. Paz, of Madrid, and very obligingly submitted to 

 me. Some of them fortunately were in alcohol, thus preserving the .'"oft parts, 

 which are of great interest. These hnve been carefully examined and described, 

 and it will be observed that the South American churacteristics of the outer 

 hard parts, as well as the included soft parts, which seem to pertain to the 

 Uniones of that continent, are here exhibited. I allude more particularly to the 

 round palpi, or mouth lips, and the d(vtrgent /(tldn of the tips of the beaks, neither 

 of which have I observed in our North American species. Very little atten- 

 tion, heretofore, has been given to the soft parts of the Unionida; of South 

 America, and none to the embryonic shell, except by myself. JI. d'Orbigny, in hia 

 Voyage dans PAincrigue Meridional, has imperfectly described and figured the 

 Boft parts of some of the genera. Spix, in his Testacea Fluviatilia Braziliensia, 

 takes no notice of the soft parts of the species, which he describes and figures 

 with much accuracy. 



Unio PECCLiARis. — Testa laevi, quadrata, compressiuscula, inaequilaterali, 

 postice obtuse angulata, antice rotunda : valvuliscrassiusculis,antice aliquanto 

 crassioribus ; natibus subpromineniibus, ad apices divaricaii uudulatis ; epi- 

 deimide virido-fusca, eradiata; deniibus candinalibus jiarviusculis, compressis, 

 obliquis, in utroque valvulo duplicibus ; lateralibus longis, lamellatis curvis- 

 que ; margarita cferuh-o-alba et iridescente. 



Embryonic Shell subtriangular, light brown ; dorsal line rather long and 

 straight ; side margins irregular and unequal — one being a segment of a 

 circle, the other an irregular curve line — forming an obtuse angle at the base; 

 basal margin obtusely angular and furnished with hooks ; granulate over the 

 whole surface. 



Hab. — South America, Don Patricio M. Paz. 



This very peculiar and unique form is now for the first time observed. Ita 

 unequal lateral margins give it an abnormal and lapsided appearance, totally 

 differing. in this from any other species known to me. 



Unio firmus. — Testa Ijevi, elliptica, subiuflata, valde inaequilaterali, postice 

 et antice rotundata; valvulis crassiusculis, antice aliquanto crassioribus; 

 natibus prominulis ; epideimide viiidi-fusca, eradiata ; dentibus cardinalibua 

 Bubcrassis, compres.= is ; in utroque valvulo duplicibus; lateralibus longis, 

 lamellatis subcurvifque ; margarita argentea et valde iridescente. 



Hab. — South America, Don Patricio M. Paz. 



Unjo rcgososclcatus. — Testa sulcata, triangulari, subinflata, subequila- 



